Brazilian gem-grade apatite (B-Ap) consists of contiguous fluorine-enriched (host-Ap) domains (∼400 nm), interspersed by isolated domains (∼200 nm) of a chlorine-enriched (guest-Ap) apatite in a long period compositional modulation. Within each of these domains a third modulation differentiating Si- and S-rich nanocrystals (5–10 nm) of ellestadite (El-Ap), a monoclinic apatite variety, developed possibly during a short term high temperature event. These unexpected miscibility gaps may be useful geothermometric tools, and could prove decisive for enhancing the properties of apatites used as heterogeneous catalysts and fuel–cell electrolytes.

A novel type of organic-inorganic hybrid zeolite has been successfully synthesized, in which lattice oxygen atoms are partially superseded by methylene groups. Various types of hybrid materials with the LTA, MFI, and *BEA structures are obtained from an organosilane in which a methylene group bridges two silicon atoms under synthesis conditions similar to those for conventional zeolites. The presence of a methylene group in the framework is demonstrated by Si-29 and C-13 MAS NMR and IR, although the Si-C bonds are partially cleaved during the hydrothermal synthesis to give rise to terminal methyl groups. The organic framework is thermally stable enough to remain after the combustion of the occluded organic structure directing agents (SDAs). The thermal stability of the organic framework is much higher than that in amorphous materials synthesized from the same silicon source and is dependent on the zeolite structures. The SDA-free materials not only show microporosity like ordinary zeolites but also exhibit distinctively high lipophilicity/hydrophobicity in a shape-selective way. These findings clearly indicate that these materials are not physical mixtures of conventional inorganic zeolites and amorphous organic-containing materials but contain true organic-inorganic hybrid zeolites.

Tin oxides, K-2(M,Sn)(8)O-16 (M = Li, Mg, Fe, or Mn), possessing the hollandite crystal structure have been synthesized and characterized by a variety of techniques, and their electrochemical behavior was studied. The compounds K-2(Li2/3Sn22/3)O-16 (K-Li), K-2(Mn2Sn6)O-16 (K-Mn), and K-2(Fe2Sn6)O-16 (K-Fe) are new phases. Rietveld refinement of the powder X-ray diffraction data showed that these Sn-hollandites exhibit a simple tetragonal structure. X-ray photoelectron spectroscopy on (K-Li) and (K-Mg) confirm formal valencies of the ions in the compounds. Galvanostatic cycling versus Li metal in the voltage range of 0.005-1.0 V at the current density of 60 mA/g showed the first cycle charge capacities of 602, 505, 481, and 418 (+/- 3) mAh/g for (K-Li), (K-Mg), (K-Fe), and (K-Mn), respectively. These values correspond to 3.7-3.0 mol of recyclable Li/mol of Sn. At the end of 50 cycles, (K-Li) and (K-Fe) performed better and retained 78 and 83% of the initial capacity. The (K-Li) also showed good rate capability. The Coulombic efficiency was > 98% between 10 and 50 cycles in all cases except (K-Mn) with the average charge and discharge voltages of 0.4-0.5 and 0.25-0.3 V, respectively. Cyclic voltammograms complement the galvanostatic results. Impedance spectral data on the (K-Li) versus Li at different voltages during the 1st and 15th discharge-charge cycle have been analyzed and interpreted.

Most partial altervalent/aliovalent substitutions for Mg or B in MgB2 studied to date depress the superconducting transition temperature (Tc) and, at higher replacements, completely suppress superconductivity of MgB2. The diminution and loss of superconductivity in MgB2 arise from the subtle interplay between the competing/cooperating effects of the electronic and lattice structural variations, which are induced by the different charge and atomic radii of the substituents. Here, we experimentally discriminate lattice structural effects from electronic contributions to superconductivity by exploiting the nanosize dependence of the lattice structure to modify structural parameters without resorting to chemical doping. It is found that the superconductivity of MgB2 is extremely sensitive to lattice parameter variation, such that contraction of Mg−Mg bond dramatically depresses Tc and eventually results in the loss of superconductivity as the average coordination of Mg to B falls from 12 to 8 due to the introduction of B vacancies for nanocrystalline MgB2 of 2.5 nm diameter.

Partial altervalent/aliovalent chemical substitutions for Mg or B have been attempted to modify the Fermi-level density-of-states and to alter the lattice parameters, thus varying the superconducting transition temperature (Tc) of MgB2. However, different from Cu oxide superconductors in which replacement of La by Y in La2CuO4 forms Y Ba2Cu3O7−δ and raises Tc from 35 to 93 K, most of the substitutions in MgB2 studied to date depress Tc, and at higher replacements completely suppress the superconductivity of MgB2. Such diminution and loss of superconductivity in MgB2 arise from the subtle interplay between the competing/cooperating effects of the electronic and lattice structural variations, which are induced by the different charge and atomic radii of the substituents. In this work, we experimentally separate lattice structural effects from electronic contributions to superconductivity by exploiting the nanosize dependence of the lattice structure to modify the structural parameters without resorting to chemical doping. It is found that the superconductivity of MgB2 is extremely sensitive to lattice parameter variation, such that contraction of the Mg–Mg bond dramatically depresses Tc and eventually results in the loss of superconductivity as the average coordination of Mg to B falls from 12 to 8 for nano-crystalline MgB2 of 2.5 nm in diameter.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Six new zirconogermanates have been prepared under hydrothermal conditions using amines as bases. There are four new structure types (ASU-n) with a common motif of ZrGe(5). ASU-23 is a layered structure: ZrGe(3)O(8)(OH)F.[C(10)H(26)N(4)].H(2)O, space group P2(1)/n, a = 6.7957(8) A, b = 12.700(1) A, c = 24.293(3) A, beta = 97.936(2) degrees, V = 2076.4(4) A(3). ASU-24 is a pillared layered structure: Zr(3)Ge(6)O(18)(OH(2),F)(4)F(2).[C(6)H(18)N(2)].[C(6)H(17)N(2)](2).2H(2)O, space group P2(1)/n, a = 7.4249(3) A, b = 25.198(1) A, c = 11.3483(5) A, beta = 90.995(1) degrees, V = 2122.9(2) A(3). This material has the lowest framework density (FD) of any oxide material that we are aware of (FD = 8.48 metal atoms/nm(3)). Two other materials form three-dimensional open-frameworks, ASU-25: ZrGe(3)O(9).[C(3)H(12)N(2)], space group P112(1)/a, a = 13.1994(4) A, b = 7.6828(2) A, c = 11.2373(3) A, gamma = 91.233(3) degrees, V = 1139.29(5) A(3). The other is ASU-26: ZrGe(3)O(9).[C(2)H(10)N(2)], space group Pn, a = 13.7611(3) A, b = 7.7294(2) A, c = 11.2331(3) A, beta = 104.793(1) degrees, V = 1155.21(4) A(3). ASU-25 is related to the mineral umbite K(2)ZrSi(3)O(9).H(2)O. The germanium equivalent has been prepared through the inorganic route: K(2)ZrGe(3)O(9).H(2)O, space group P2(1)2(1)2(1), a = 13.6432(6) A, b = 7.4256(3) A, c = 10.3973(4) A, V = 1053.33(8) A(3). The structural relationships between ASU-25 and its inorganic counterpart are described. The thermal decomposition of the germanium umbite generated the cyclic trigermanate K(2)ZrGe(3)O(9), analogue of the mineral wadeite, crystallizing in the orthorhombic system, a = 7.076 A, b = 12.123 A, c = 10.451 A, V = 904.5 A(3).

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Three new germanate solids, ASU-19, ASU-20-DAPe, and ASU-20-DACH, have been synthesized under hydrothermal conditions using respectively 1,4-diaminobutane (DAB), 1,5-diaminopentane (DAPe), and 1,4-diaminocyclohexane (DACH) as bases. The structures of ASU-19 and ASU-20-DACH have been characterized by single-crystal X-ray diffraction: ASU-19, Ge14O29X4.[GeOX2].[H(2)DAB](3).3.8H(2)O (X = F or OH), space group P (1) over bar, a = 11.4191(5), b = 12.05250, c = 18.1847(8) Angstrom, alpha = 90.704(1)degrees, beta = 92.635(1)degrees, gamma = 91.389(1)degrees, V = 2499.1(2) Angstrom(3); ASU-20-DACH: Ge7O14X3.[H(2)DACH](1.5).2H(2)O, space group C2/c, a = 15.9525(11), b = 17.5476(12), c = 19.0027(13) Angstrom, beta = 109.446(1)degrees, and V = 5015.90 Angstrom(3). The structure of ASU-20-DAPe, Ge7O14X3.[H(2)DAPe](1.5).H2O, has been determined from X-ray powder diffraction data: space group C2/c, a = 16.3180(5), b = 16.6125(4), c = 17.8898(6) Angstrom, beta = 99.684(2)degrees, V = 4780.5(3) Angstrom(3). All three structures are based on the assembly of the same cluster Ge-7(O,OH,F)(19). The two ASU-20 structures consist of a slab of four-connected clusters. In ASU-19, the same layers are connected pairwise through a GeO2X2 spacer, generating a slab structure, with slab thickness ca. 20 Angstrom. The existence of the same layer in the presence of three different organic bases shows the adaptability of the structures to molecules differing in size, shape, and symmetry.

The reaction of pentaerythritol and tetraethylorthocarbonate at 260 degrees C for 12 h yields a white crystalline material that was characterized by 13C CPMAS NMR, CHN analysis, FT-IR, electron and X-ray powder diffraction, and Rietveld analysis. The white crystalline material was found to have the formula C6H8O4 and a crystal structure with a monoclinic cell [a = 9.167 A, b = 5.681 A, c = 5.880 A, beta = 90.0 degrees , space group I2] of hexagonally arranged spiro-oligomeric chains.

A new 1,4-diazabicyclo[2.2.2]octane (DABCO)-based quaternary ammonium compound is designed, synthesized, and used as structure-directing agent (SDA) for molecular sieve synthesis. Several 1,1'-alkylenedi(4-aza-1-azonia-2,5-dimethyl-bicyclo [2.2.2] octane) type SDAs are used in all-silica synthesis mixtures. Among the SDAs tested, the use of 1, 1'-butylenedi-(4-aza-1-azonia-2,5 5-dimethylbicyclo[2.2.2]octane) gives a new phase (GUS-1), whereas the use of other SDAs gives zeolite beta ((*)BEA), ZSM-12 (MTW), and ZSM-5 (MR). The GUS-1 is indexed in the orthorhombic crystal class with refined lattice constants a = 16.4206(4) Angstrom, b = 20.0540(4) Angstrom and c = 5.0464(1) Angstrom. The crystalline architecture of GUS-1 shows the same [001] projection of the framework as that of mordenite (MOR), and is characterized by a one-dimensional 12-membered ring channel system that is closely related to the channels of ZSM-12. The GUS-1 is stable to heat upon calcination at 700 degreesC in air. The calcined material exhibits adsorption capacity that is comparable to typical large-pore one-dimensional microporous silicates. The behavior of the SDA during synthesis is also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

Synthesis conditions for an MTF-type zeolite UTM-1 have been studied and this material has been characterized in detail. UTM-1 is crystallized in the presence of hexamethyleneimine (HMI) under the synthesis conditions similar to those of MCM-22 but from mother gels with high SiO2/Al2O3 ratio at a narrow range of synthesis temperatures. The crystal growth of UTM-1 proceeds quite rapidly after a long induction period in contrast to the gradual crystal growth of MCM-22. Through the optimization of synthesis conditions, pure silica and Ti-incorporated materials with the MTF structure can be easily synthesized in the hydroxide media without employing any co-template other than HMI. UTM-1 is proved to have strong acidity comparable to that of ZSM-5 having a similar SiO2/Al2O3 ratio, presumably reflecting their structural similarity. UTM-1 has large outer surface area so as to show high catalytic activities in reactions occurring at the outer surface of the catalyst, whereas its small pore aperture restricts the diffusivity of reactant molecules into the pore system.

A tiling of space by tiles that have all hexagonal faces and are infinite in one direction is described. The tiling is simple (four tiles meet at each vertex, three at each edge and two at each face) and carries a 4-connected net whose vertices are the lattice complex S* with symmetry Ia(-)3d. The tiling is closely related to the densest cubic cylinder packing, Gamma. It is shown that the other invariant cubic lattice complexes unique to Ia(-)3d (Y** and V*) are also related to the same cylinder packing.

This chapter describes the synthesis of a new microporous silicate using 1,4 diazabicyclo[2.2.2]octane (DABCO)-based structure-directing agent (SDA). Results of the synthesis and structure determination are discussed. The behavior of the SDA during synthesis is also presented.

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Parallele hexagonale Prismen von Cancrinit (CAN), deren Kanäle senkrecht zur Substratoberfläche angeordnet sind, entstanden beim heteroepitaktischen Aufwachsen auf millimetergroße Sodalit(SOD)-Einkristalle. Das Experiment basiert auf einem Modell, in dem die ABABAB-Stapelfolge entlang der [0001]-Richtung von Cancrinit mit der ABCABC-Folge entlang der 〈111〉-Richtung von Sodalit verknüpft wurde (siehe schematische Darstellung).

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA Flexible Germanate Structure Containing 24-Ring Channels and with Very Low Framework DensityJacques Plévert, Travis M. Gentz, Aaron Laine, Hailian Li, Victor G. Young, Omar M. Yaghi, and Michael O'KeeffeView Author Information Department of Chemistry and Biochemistry Arizona State University, Tempe, Arizona 85287-1604 Department of Chemistry, University of Minnesota Minneapolis, Minnesota 55455 Department of Chemistry, University of Michigan Ann Arbor, Michigan 48109-1055 Cite this: J. Am. Chem. Soc. 2001, 123, 50, 12706–12707Publication Date (Web):November 17, 2001Publication History Received3 September 2001Published online17 November 2001Published inissue 19 December 2001https://pubs.acs.org/doi/10.1021/ja016996ahttps://doi.org/10.1021/ja016996arapid-communicationACS PublicationsCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views1365Altmetric-Citations144LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Cluster chemistry,Germanium,Materials,X-rays,Zeolites Get e-Alerts

Six packings of symmetry-related cylinders, with cylinder axes in invariant positions (coordinates completely determined by symmetry), are described. Two have axes along [100] and four have axes along [111]. It is shown that there can be no cubic cylinder packing with axes along [110]. Earlier errors concerning the numbers of such packings and their symmetries are corrected.